The invention pertains to conveyor motion sensing apparatus employing a traction wheel engaging a moving conveyor wherein the traction wheel housing is self-cleaning and the traction wheel is biased by spring means toward the conveyor.
In the handling of bulk materials in grain elevators, feed mills, coal mining and processing installations, and similar applications wherein belt conveyors are utilized, it is critical that the proper operating conditions of the conveyors be maintained during operation. The conveyed material is often transferred from one conveyor to another, and if the receiving conveyor has slowed from its designed rate of movement the conveyor will quickly overload, and may clog or otherwise malfunction resulting in damage to equipment and extended downtime for repair.
To protect conveyor systems against overloading, motor burnout and other malfunctions, it is common practice to use motion sensing devices directly associated with the conveyor which continuously sense the rate of conveyor movement, and if the rate of conveyor movement varies from a predetermined standard an alarm is energized or other control function actuated to indicate to the operator that immediate attention is required, and, in many cases, an entire conveyor system may be automatically stopped in the event one of the conveyors slow a predetermined degree. Usually, such safety devices either employ a traction wheel engaging the conveyor itself, or the motion sensing apparatus is connected to and directly driven by a conveyor roller, drive shaft or idler shaft.
Safety requirements of some states dictate that conveyor motion sensors directly indicate the rate of conveyor movement and sensors connected to roller shafts are not acceptable. In such instances traction wheels engaging the moving conveyor are employed, and apparatus of this type is disclosed in the assignee's prior U.S. Pat. No. 4,119,055. One of the problems attendant with directly engaging the moving conveyor lies in the fact that the position of the conveyor belt will often vary during use due to variations in belt tension as the load carried by the belt varies in accord with the amount of material being conveyed at any given time. Such conveyor displacement may permit the conveyor to move away from a frictional engagement with the motion sensor traction wheel rendering the motion sensor inactive and permitting a false signal that the conveyor has stopped resulting in unnecessary conveyor deenergizing and other complications.
Additionally, as the material being conveyed usually consists of relatively small particles, such particles will often fall into the traction wheel housing due to its proximity to the conveyor, and it is possible for the traction wheel housing to become clogged with such foreign matter and render the sensing apparatus inoperative. Such deficiencies are present in the assignee's apparatus as disclosed in the above mentioned patent.